Image control device with means to precharge the printing gap



May 30 1957 J. E. MaCGRlr-F 3,323,131

IMAGE CONTROL DEVICE WITH MEANS TO PRECHARGE THE PRINTING GAP Filed Aug.17, 1962v sheeLS-Sheet l`- Mull 5 El ,3c INVENTOR. Jj Jack f. nume/FF.'

yMay 30, 1967 .E. MaCGRn-F 3,323,131

IMAGE CONTROL DEVICE. WITH MEAN-S TO PRECHARGE THE PRINTING GAP:

Filed Aug. l?, 1962 .f5 Sheets-Sheet 2 INVENTOR. JAC/f E. M46 @1e/PF.

Galand, /Zmnw/ #M May 30, 1967 J. E. MaOGRlr-F 3,323,131

IMAGE CONTROL DEVICE WITH MEANS TO PRECHARGE THE PRINTING GAP Filed Aug.17, 1962 v 5 Sheets-sheet INVENIOR. .//CA/ Mac @eff/ United StatesPatent O 3,323,131 IMAGE CON'IRI. DEVICE WITH MEANS T0 PRE- CHAR-GE THEPRINTING GAP Jack E. MacGriif, Redford, Mich. (17255 Lalser Road,Detroit, Mich. 48219) Fixed Ang. i7, 1962, ser. No. 217,725 6 Claims.(Cl. 346-74) This is a continuation-in-part of my co-pending applicationNo. 693,690 filed Oct. 31, 1957 now Patent 3,056,- 136 of 1962, on animage control device and method of printing, which is acontinuation-in-part of application No. 410,090 filed Feb. 15, 1954,which latter application is now abandoned. Y

This invention relates to an image control device, a method ofprinting,V and more particularly to a sensitive image control deviceresponsive to variations in light intensity focused from an image and inits responses t-o such variations adapted to control the flow ofelectrons to form an electrostatic pattern, and for control ofdeposition of charged pigment particles to form a visible image.

It is the object of the present invention to provide an improvedsensitive image control mechanism.

It is the further object of the present invention to provide an improvedand novel image control device for forming electrostatic patterns on amoving web of image receiving material, and to further make saidelectrostatic patterns visible by the deposition thereon of chargedparticles of finely divided pigment, with the amount of depositioncontrolled by variations in light intensity from an image to be printedfocused upon the photosensitive portion 4of the image control device.

These and other objects will be seen from the following specication andclaims in conjunction with the appended drawings in which:

FIG. l is a side elevational view of an electron emission c-ontroldevice.

FIG. 2 is a fragmentary plan view thereof.

FIG. 3 is a fragmentary view, si-milar to FIG. 2 showing the emissionconductors extending past the end of the support.

FIG. 4 is a side elevational View of the present control device,accelerating electrode, light source and electrical connections.

FIG. 4a is a perspective view on an enlarged scale of the light shieldof FIG. 4.

FIG. 5 is a side elevational view of another form of control device as amodification of FIG. 4.

FIG. 6 is a fragmentary section taken on line 6 6 of FIG. 5.

FIG. 7 is a perspective view of another form of control device.

FIGS. 8a through 8d are progressive diagrams illustrating the forming ofa unilateral rectifying junction layer upon the conductors of thecontrol device.

FIGS. 9a, 9b and 9c are respectively fragmentary elevational, plan andperspective views showing the unilateral junction layer formed `over theconductors of an image control device.

FIG. 9d shows the same layer as formed within a depressed area of theinsulating base.

FIG. 10a is a fragmentary elevational view showing one of the series lofbias emission conductors overlying the conductors of an image controldevice fragmentarily shown.

FIG. 10b is a perspective View of the series of bias emissionconductors.

FIG. 11a is similar to FIG. 10a showing one type of hot cathode type ofbias e-mission conductors.

FIG. 11b is a perspective View of said type of bias emission conductors.

ICC

FIG. 12 is a fragmentary schematic side elevational view of another formof image control device.

FIGS. 13a through 13d are fragmentary plan views showing different formsof emission conductors.

FIG. 14 is a fragmentary Aperspective view of another form of emissioncontrol device.

FIGS. 15a through 15e are respectively fragmentary, plan elevational andside views of the accelerating electrode of FIG. 14.

FIG. 15d is a fragmentary plan View corresponding to FIG. 15a.

FIGS. 16a, 16b, and 16e are respectively fragmentary plan, side andfront elevational views of the insulating -base and conductors shown inFIG. 14.

FIG. 17 is a schematic view of the image control device substantially asshown in FIG. 14 illustrating its mode of use for forming electrostaticimages or patterns on a receiving surface and the mode of transmittingimages to the light sensitive control device and for rendering saidimages visible. i

FIG. 18 is a fragmentary perspective and schematic view of another formof control device.

FIG. 19 is a schematic illustration similar to FIG. 17 showing anotherembodiment andmode of printing.

FIG. 20 is a schematic view of a wiring diagram and circuitry of amodified image control device of increased sensitivity.

FIG. 21 is a fragmentary plan View taken in the direction of the arrowsZ1 in FIG. 20.

FIG. 22a is a fragmentary elevational view of the image control deviceshown in FIG. 20.

FIG. 22b is a fragmentary elevational view illustrating the relationshipbetween the conductors 2 and 70 of FIG. 20. v.

FIG. 23 is a fragmentary side elevational view of a modiiication of thepresent control device.

FIG. 24 is a similar view of the control device of FIG. 18 with thecircuits fragmentarily shown.

FIG. 25a is a fragmentary perspective view of a wedgeshape form ofreceiving electrode.

FIG. 25b shows the same electrode with curved receiving edge forengagement with the adjacent image web.

FIGS. 26-27 are plan, elevational views of another means of supplying abias potential. j l

It will be understood that the above drawings illustrate merely `severalpreferred embodiments of the invention, and that other embodiments arecontemplated Within the `scope of the claims hereafter set forth.l A' v.In my co-pending application No. 693,690, the printing apparatus has anelectronic image control device as illustrated in FIGS. 1 and 2 ofthis'application, and generally designated at 35, which includes anon-electrically conductive insulating base 1, which may be glass,plastic, or any non-electric conducting material; and mounted thereonare a plurality of horizontally disposed parallel spaced conductors 2arranged in a rowQTh'ese are .001 to .005 inch wide and spaced apart to500 per lineal inch. These are secured to the base inV insulated spacedrelation to each o-ther.

A light-sensitive layer 4 is mounted over conductors 2 and in contacttherewith, said light-sensitve fil-m being made from selenium, forexample, which has a relatively high electrical resistance and has acharacteristic of changing its electrical resistance when' exposed tolight;

This image control device 35 is shown in elevation on an enlarged scalein FIG. 1, whereas FIG. 2 is a fragmentary plan view thereof.' f

Mounted upon the light-sensitive layer 4 and in contact therewith is atransparent electrode layer 5, which is adapted for connection by thewire lead 30 to a suitable source of current. Mounted over thetransparent electrode layer 5 and in longitudinal alignment withinsulating cover 3 is a transparent protective -c-overing layer 6 tocomplete the image control device 35.

The transparent electrode layer 5 may be a thin evaporated transparentiilm of an electrically conductive metal such vas platinum, silver, orstannous cloride, for example. Transparent electrode layers are wellknown. By transparent electrode layer is meant a layer of electrodematerial that is transparent to the radiation of portions of theelectro-magnetic spectrum extending from the infrared through theultra-violet. Thhis electrode layer must be transparent or translucentto light so that variations in light intensity of an original image willcontrol the electrical conductivity of the light-sensitive layer 4 inFIG. 1.

In my copending application 693,690, in order to form electrostaticpatterns with the device of 35, the image 7 sought to be reproduced isaffixed or otherwise secured to the outer surface of the rotatable drum8, which has a central axis of rotation 22, such as is in FIG. 17herein.

The light 9 upon the exterior of drum 8 illuminates a strip of image 7,and this illuminated strip or the image 19 thereof, is projected by thelens 10 through a horizontally elongated slot 28 of light shield 18,FIGS. 4 and 4a, and thence to the direction changing mirror 11.

The image 7 is thus projected through transparent cover 6, through thetransparent electrode layer 5, and onto the light-sensitive layer 4 forregulating the internal resistance thereof and in turn controlling thequantity and flow of electrons through the respective conductors 2 fromthe current lead 29 as in FIG. 17 which is connected to the electrodelayer 5. It will be understood that the mirror could be eliminated wherethe image line 7 is so arranged as to be focused -directly upon thelight-sensitive layer, such as the image line 36, illustrated in FIG. 2of my original co-pen-ding application, Ser. No. 693,690.

A moving web of paper or other image re-ceiving material 12 extendsaround and passes over the revolving drum 13, the axis of rotation ofdrurn 13 being parallel to the axis of rotation of drum 8.

As shown in FIG. l of my original co-pendin-g application, and as inFIG. 17 herein, in the event that a transparent image 7 is employed uponthe drum 8, the light source 9 may be positioned upon the interior ofdrum 8, rather than the exteriorally arranged light 9, which is adaptedfor use in conjunction with opaque images.

In my original co-pending application, the outer ends of conductors 2,corresponding to conductor 2 herein, may extend outwardly beyond the endof the image control device 35, FIG. 1, and lie in aplane parallel todrum axis 21, the same ends of said conductors :being spaced a shortdistance, for example, approximately 0.001 to 0.010 inch from moving web12, FIG. 17. There is provided a stationary electrode blade or comb 14,which has a horizontally disposed thin elec-tron receiving edge 23,Which is preferably formed with a series of longitudinally spacedcomb-like projections 24, FIG. a. The number of projections per inch isthe same as the number of emission conductors 2 per inch, as indicatedin FIG.` 5 of my original co-pending application No. 693,690, said bladebeing connected to the return wire lead 31 similar to what is shown inFIG. 17, for completing the high voltage circuit. Said electrode blade14 of FIG. 1 of my original copending application is shown on an`enlarged scale in FIG. 4 of that application and FIG. 5 is afragmentary bottom plan view thereof showing comb-like projections 24.

In operation of my original device in application 693,- 690, light 19from the image 7 falling upon the lightsensistive surfaceY 4 changes theelectrical resistance of the photo-conductive material between thetransparent electrode 5 and the individual emission conductor oppositethereof 2, permitting electrical discharge from the emission end of saidconductor across the space in the direction of the receiving electrode14.

In operation, the voltage necessary to provide said emission must be inexcess of the ionization potential of the system consisting of theemission conductor 2, the receiving electrode 14, the image web 12, andthe space between.

After this system Iis brought to ionization potential, voltage in excessof this level will permit discharge or liow of electrons from theemission ends of conductors 2, said excess voltage being the signalpotential.

It is the object of this invention provide an improved .image controldevice that provides a constant bias voltage that retains the systemconsisting of the emission conductor 2, the receiving electrode 14, theimage receiving web 12 and the space between at a level not quite equalto the ionization potential of said system, with the signal voltagecorresponding to the light received from the original image 7 being inexcess of this bias ionization volage.

FIGS. 1 and 2 of this application correspond to FIGS. 6 and 7 ofmy'original co-pending application 693,690.

FIG. 3 shows how the electron emission conductors 2 can extend past theend of the insulating supporting base 1, if desired, as shown at 58.

It is contemplated in this invention that the parallel electron emissionconductors 2 Will be retained at the potential not quite equal to theionization potential of the system previously described, said potentialbeing supplied by an electron emission source Separate from thelight-controlled photo-conductive surface Which supplies the signalpotential to said emission conductors.

FIG. 4 shows such a device.

Spaced parallel emission conductors 2 are retained on an insulatingnon-electrically conducting base 1. A photoc-onductive layer 4 isaffixed in contact with said conductors, and a transparent electrode 5positioned over the photoconductive surface. A wire lead 30 connectssaid transparent electrode with a source of potential.

A layer 40 is also positioned over the conductors 2, said layer beingconnected through an electrode layer 41 yand a conductor 42 to a sourceof bias potential.

Said layer 40, while supplying bias potential to the individualinsulating conductors 2, through unilateral rectifying junctions,retains said conductors 2 in insulated relation to each other.

FIG. 5 is another such device, with the photoconductive layer 4 being`affixed to one side of the conductors 2, and the bias potentialunilateral rectifying junction layer 40 being applied to the other sideof the conductors. This device is generally designated as 69.

A method of forming the layer upon the conductors is shown in FIGS. 7and 8a through 8d.

In FIG. 7, the insulating base 1 has 'a depressed area on which thetransparent conductor 5 is alixed. The light sensitive layer, here shownas a multiple-layer configuration p,n,p, is affixed on top of thetransparent conductor, and the individual discharge conductors 2 placedon top of the light sensitive layer. FIG. 7 shows how a single ormultiple-layer photo-conductive control can be devised underneath theparallel conductors 2.

FIGS. 8a through 8d show how unilateral rectifying junctions can also bepositioned underneath the conductors. Photo-conductive junctions may beformed in a similar manner.

A conducting electrode 41 is positioned on top of a depressed area ofthe insulating base 1. A semi-conductor 40 is positioned on top of theconducting layer, with a doped surface 42. Conductors 2 are formed -ontop of this surface by photo-etching as is well known in the art, and asis described in my co-pending application 693,690.

The areas 43 between the individual conductors 2 in FIG. 8b are etchedout, leaving unilateral rectifying junc.- tions 42 between thesemi-conductor 40 and the conductors 2.

This area 43 can be filled with an electrically insulating material,such as glass, plastic, etc., as at 44 in FIG. Sc.

A photo-sensitive layersuch as selenium, for example, can be formed overthis structure as in FIG. 8d, shown at 4; the transparent conductor S,and an insulating cover 3 may be placed over that. This forms a deviceas is shown in FIGS. 5 and 6.

Either the light-sensitive layer, or the bias-supply layer can be formedrst, conductors formed, and the other layer applied last, depending uponthe structure desired.

The bias potential supplied to the emission conductors 2 can be suppliedeither through a semiconducting unilateral connecting layer 40 as shownin FIGS. 4 through 8, or through a discharge potential in a vacuum.

FIGS. 9a, 9b and 9c show the unilateral layer 40 formed over theconductors 2. In FIG. 9d, this layer is formed in a depressed area inthe insulating base 1.

In FIGS. 10a and 10b, a potential is connected through Wire 42 to aseries of interconnected emission conductors 24, said conductors beinginterconnected by the strip 53. These conductors can be formed byphoto-etching a continuous conducting layer on the insulating base 51,as is well known to those versed in the art.

When positioned over the electron emission conductors 2, in a vacuum,the discharge as at 57 occurs when the unit, generally indicated at 61,is properly connected to a source of potential. This is a cold'cathodedevice.

A hot cathode device is schematically shown in FIGS. lla and 11b, with aheater, 54, maintaining the cathode 55 at a predetermined temperature.Electron control shield 56 directs the electron emission 57 towards theelectron emission conductors 2.

Such a device is lshown in FIG. 12, with the hot cathode devicegenerally designated as 59 shown inside `a chamber 50', in which ismaintained a vacuum.

The chamber 50 is sealed to the electron emission conductors 2 andinsulating base 1' by the insulating iillet 65 which can be lowtemperature sealing glass applied as a frit and fused by heat.

The light-sensitive layer 49 shown here affixed to the transparentelectrode 5, is retained in a vacuum inside transparent chamber 5t),with the discharge at 60 controlled by the light source 19. Theaccelerating electrodes 14 and 14' designate this device as adouble-ended unit which will control the formation of two electrostaticpatterns at the same time on the image transversely movable webs 12 and12'.

The conductors 2 of the device shown in FIGS. 1, 2, 4, 5, 6, 7 and 8,have generally been designated as parallel emission conductors. Theseare shown in FIG. 13a. The shape of these conductors can be varied, asshown in FIGS. 13b through 13d.

The electron emission ends of the conductors are generally designated at76, with the general designation of 80 being the photoconducting surfaceand the transparent electrode.

In FIG. 13b, the area under the photoconductor, generally designated at45, is wider than the electron emission conductor 2. The distancebetween the emission ends of the conductor, here designated as A and B,must have the same ratio of distance as that under the photoconductor asa and b. Y

In FIG. 13C, the part of the conductor under the photosensitive surfaceis diamond shaped, and in FIG. 13d the emission ends of the conductorsat 76 are smaller than the parts of the conductors generally designatedas 47, under the light sensitive surface.

By proper design lof the emission conductors 2 in relation to the partof the conductor -under the photosensitive surface, the inter-electrodecapacitance and light-sensivity of the electron emission control devicecan be varied. Such a device as has been described can either be a solidstate semi-conducting assembly, or an electron-discharge device whichoperates in a vacuum.

A vacuum device, different from the one described in FIG. 12 is shown inFIG. 14. A hollow glass tube 50 is slotted. An Yinsulatingnon-conducting base 1 on which are aixed emission conductors 2', ispositioned in the slot so that the emission ends of the conductors 2 areoutside of the vacuum chamber. A series of electron emission conductorson the device generally designated at 61, Iand formerly described inFIGS. 10a and 10b, are positioned over the electron emission conductors2 so that the emission conductors receive electrons from the device 61which is connected through the wire 42 and the directional diode 63 to asource of potential.

A light-sensitive emission source, generally designated at 35 anddescribed in FIGS. l and 2, is positioned with the electron emissionconductors of said device respectively in contact with the conductors 2.An insulating electron shield 62 is placed between the two emissionsources.

Fillets of low temperature sealing glass 65 fuse the electron emissionconductor assembly to the vacuum chamber, and the interior units arepositioned and affixed in a manner well known to those skilled in theart.

The transparent electrode of the device 35 is connected to a source ofpotental by lead 29, and the exterior accelerating electrode 14 is alsoconnected by lead 31 as shown in the diagram FIG. 14.

In operation, light 19 fai-ling on the light-sensitive portions of theemission control 35 permits electrons to be discharged to individualemission conductors 2 depending upon where the light falls; -at the sametime, lall electron emission cond-uctors 2 receive a bias potential fromthe device 61.

Because the signal potential from the conductors of the device 35 is inexcess of that potential supplied by the device 61, individual emissionconductors 2 are raised to a potential equal to the sum of the voltagessupplied. Thus the emission conductors 2', the accelerating electrodegenerally designated at 14, and a space between are retained at thepotential controlled by the device 61, with a variable signal potentialsupplied by the device 35 controlling the electron discharge betweenends of individual emission conductors 2 and the accelerating electrode14.

The accelerating electrode at 14 can be fashioned as shown in 15athrough 15d, -with individual conductorsZS iconnected by a conductingstrip 53 lphoto-etched on an insulating base 51 in a manner well knownto those skilled in the art. These emission conductors can extend pastthe ends of the insulating base as shown in FIG. 15d, at 58. Theelectron emission conductors of the device shown in FIG. 14 can befashioned in a manner well known to those skilled in the art, as shownin FIG. 16a throug-h 16C, with the conductors photo-etched, from .aconducting layer applied to a non-conducting insulating base 1.

FIG. 18 and FIG. 24 show still another -concept of the control device,with the bias voltage supplied 'by vacuum discharge from the devicegenerally designated at 61, said discharge being shown at 59. The signalvoltage is supplied through the semi-conducting photo-sensitive layershown at 4, and the transparent electrode 5. A vacuum 64 is retainedinside of the transparent housing 50. The device of FIG. 14 is shown in:operation in FIG. 17. This is similar to the device described in FIG. 1of my original co-pending application 693,690 except that the part 81 issubstituted for the part generally shown at 35 in the originalapplication. Rectilinear strips of light 7 from the image 7 are focusedthrough the lens 10 onto the photo-sensitive surface of the device 35.An emission of electrons to individual conductors 2', as shown at '60,is controlled by the light.

The conductors 2', the accelerating electrode 14, the image receivingweb 12, the space between are retained at a level not quite equal to theionization potential system 'by the device generally designated at 61,connected through wire 42 and the unidirectional diode 63 to a source ofpotential. As the drum 8 is rotated in synchronization with the drum 13,and the original image Web y68 is moved in synchronization with theimage receiving web 12, an electrostatic pattern is formed on image web12 corresponding to the original image 7. This electrostatic pattern canbe made visible by particles of charged '7 pigment supplied from apigment generator 16, conduit 25, and a blower 17.

The electron emission control device can be controlled by light `imagesfrom more than one master image at the same time. In FIG. 17, lens 10and lens 10 `and lens 10", for example simultaneously focus light images19, 19 and 19" respectively on the light-sensitive layer of part 35.Light focused by lens 10 and lens 10 is fed through a mirror -which bothreflects light and transmits it, and light from lens 10 is fed through aprism, for example, to show two modes of operation.

By this arrangement, the electron emission control conductors 2 in FIG.17 are lactuated by the sum of the light from all sources falling on thephoto-sensitive surface lying between the transparent electrode and theadjacent emission conductor, and the electrostatic pattern formed onimage receiving surface 12 is a combination or montage of all masterimages.

If desired, this electrostatic pattern can be made visible at a laterspot, by particles of charged pigment capable of Ibeing deposited uponan electrostatic pattern, as shown at 66. The method of developingelectrostatic patterns is well known to those versed in the art.

At station 67, the pigment deposited on the electrostatic pattern atstation. 66 can be fused to the web lby heat, chemical, or other means.

Still another embodiment of this invention is shown in FIG. 19. A devicesuch as described in FIGS. 4, 5, and 6, generally designated at 69, ispositioned in proximity to a drum assembly Which Ihas a layer 71,capable of retaining electrostatic charges, affixed to the conductingdrum 72.

As light from an image affixed to drum 8 is reilected through the lens10 and mirror 11 to the photo-sensitive surface of the device 69, anelectrostatic pattern is formed on the surface 71 of the drum. As thedrum 72 rotates in synchronization with the drum 8, and the image web12, particles of charged pigment, generally designated at 73 are affixedto the electrostatic pattern on the surface 71 of the drum. As the drum72 rotates, the pigment particles which are affixed at station 73 aretransferred to the image web 12 due to the potential difference betweenthe drum and the transfer drum or electrode 13.

A suitable means for erasing the electrostatic pattern and any particleswhich adhere to the drum surface 71 before the next rotation can beprovided, as is well known to those skilled in the art, and can consistof fur brushes, corona discharge, or other means.

The advantage of a system show in FIG. 19 is that the variations inimage Web 12, such as are found in paper, plastic, etc., do not affectthe formation of the original electrostatic pattern, since theionization potential between the drum 71-72 and the device 69 isconstant.

Another method for providing bias potential is shown in FIGS. 26 and 27.Bias conduct-ors generally designated at 77 are positioned between eachemission conductor `2. Said conductors 77 are interconnected by aconducting strip 78 and to a source of bias voltage, so that all areretained atY the same potential. An insulating layer 79 over each biasconductor isolates it from the photo-sensitive layer 4 and thetransparent electrode 5 which supply the signal potential to theelectron emission conductors 2.

-In such a device, the bias emission conductors and the electron signalemission conductors alternate, and by suitable connection in a circuitprovide control of the ionization level of the device and the spacebetween the electron emission ends and the image receiving web. Such anarrangement also isolates the electron emission conductors 2 from eachother and can be used to control the inter-electrode capacitance effect.

A method to increase the sensitivity of an image control device is shownin FIGS. 20, 21, 22, and 23. FIG. 20 is a schematic view of the cirouitinvolved. A row of electron emission conductors 71, are retained ininsulated spaced relation to each other, FIG. 21. An acceleratingelectrode generally designated at 14 and an image receiving web at 12Iare similar to those already described.

A series of bias emission conductors generally designated at 52 maintainthe electron emission conductors 71, the web 12, the acceleratingelectrode 14- and the space between at a potential not quite equal tothe ionization level of the system. Y

A series of electron emission conductors which are retained in the sameparallel spaced relation as the electron emission conductor-s '71, arepositioned so that the emission ends of conductors 71B` will supplyelectrons to the conductors 71 in absence of any control field 4,3.A

The image control device generally designated at 3,5, which has a seriesof parallel emission conductors retained in spaced relation to eachother, generally designated at 2, is positioned so that the emissionconductors 2 are in proximity to the emission ends of conductors 70 andthe receiving ends of conductors 71.

The image control device 35 is shown in FIGS. l and 2, and has beendescribed before, with a photo-sensitive layer applied across theconductors and a transparent electrode over that. The emission ends ofthe conductors 2 can be positioned as shown in FIG. 22a, between thesets of parallel conductors A and B. (Letters A-B in FIG.

2O designate a system comprising an emission conductor 70, acorresponding electron emission conductor 71, and the receivingelectrode 14. The designation C-E is the same as the C-E shown in FIG.20, of the emission control conductor y2.)

So the ends of these conductors 2, shown at 58 can be between the gapswhich are between the conductors 70 and 71, or close to them, as shownin FIGS. 22a and 22h.

A plan view taken on line 291-21 of FIG. 20 is shown in FIG. 21.

The conductor C-E is the control conductor. Each system compri-sing abias conductor 52, shown at D, the emission conductor 71, and the signalsupply conductor 711, is numbered 1, 2, 3, y4, as consecutive systems ina row.

All of the signal supply conductors 741 are interconnected and retainedat the same potential.

Depending upon the light received by the device 3S in proximity to anyelectron emission conductor 2, said conductor 2 voltage varies.

. Because the potential supplied to the conductors 2 is more negativethan that supplied to the emission conductors 7d, light which permits adischarge from the transparent electrode to the emission conductor 2 onany particular row, for example, that shown in row 3 in FIG. 21,establishe-s a field 43 which inhibits emission of electrons fromconductor 70, row 3, to conductor 71.

The device 35 acts like a control grid between the cathode 711 and thereceiving conductor 71 which might Ibe termed .the plate in a triodedevice. The device 52 and the conductors 71 could also be termed a diodedevice. So the device in PIG. 20 and 21 could be termed a diode-triodeemission control device.

One configuration of this is shown in FIG. 213. Parallel emissionconductors 71 and 70 are formed on an insulating base 73 in a mannerwell known to those skilled in the art, and can be formed byphoto-etching, etc. These conductors can be formed as one conductor, andthen a gap as shown at 75 machined in the plate.

Parallel insulated conductors are formed on both sides of an insulatingmedium 74, as shown at 5-2 and 2. The conductors 52 become the biasconductors, and the conductors 2 the signal control or grid conductors.

A light-sensitive l-ayer 4 and a transparent electrode 5 complete thedevice, which is enclosed in a transparent tube of insulating material,such as glass, 50. A vacuum is maintained as shown `at 64.

With suitable connections to the device and an accelerating electrodegenerally designated at 52', the emission ends 76 of the electronemission conductors 71 are retained at a potential determined bytheelectron emissions from conductors 52 which are connected through Wire42 Vand unilateral diode 63 to a source of potential. Light falling onthe photo-sensitive surface inhibits electrons from the signal source70, and no discharge occurs from 76 to the receiving electrode 52'.

Absence of light over the photo-sensitive -surface at any electronemission conductor 2 decreases the control iield and permits dischargefrom corresponding conductors 70 to corresponding conductor 71,increasing the potential on the emission end of the conductor 76 abovethe ionization level of the system consisting of the emission conductor76, the accelerating electrode 52', the space between, permitting adischarge at that particular spot.

The wedge-shaped electrode 52' is shown in FIG. 25a, with the electronreceiving edge 23 :and the wire connection 31 to the source ofpotential.

F-IG. 25h shows that this electron receiving edge 23 can be a roundedsurface of a small diameter, for example, 0.001 inch to permit directpassage of an image web 12 over said electrode without a revolving drumbeing positioned between the accelerating electrode of the image controldevice.

These image control devices may control two images at once, as in thedevice shown in FIG. 24. It is contemplated that the photo-sensitivesurface, which varies in electrical resistance as light strikes it, canbe la single layer surface such as selenium, or a multiple layer surfacesuch as a doped p,n,p germanium, doped silicon, or other multiple-layerphoto-conductor, as are well known to those skilled in the art.

The original image 7 can be wrapped around the drum 8, or can be passedas a continuous web as shown at 68 in FIG. 17.

It is contemplated that the semi-conductor which furnishes theunilateral potential to the electron emission conductors 2, as shown inFIGS. 4, 5, 6, and 8a through 8d, can be -a multiple layer configurationwhich provides a source of potential to each conductor, but retains themin insulated spaced relation.

For the device as shown in FIG. 17, and a spacing between the emissionends of the conductors 2 and the image web 12 of about 0.001 inch, theionization level of the system consisting of the emission conductor, theaccelerating electrode, the image web `and the space between may be inthe order of 600 to 800 volts.

The extra signal level necessary to provide emission from the ends ofthe conductors 2' and form an electrostatic pattern on the surface ofthe Iimage web 12 may be from 20 to 200 volt-s, depending upon thematerial of the image web and the electrostatic pattern desired.

In the device shown in FIGS. 20, and Z3, the potential across thephoto-sensitive layer 4 is only a fraction of the signal voltagesupplied by the signal emission conductor 70 to the electron emissionconductor 71.

In the original device shown in FIG. 1 and FIG. 2, the ionization levelpotential plus the signal level potential must both come from theconnection 30 through the transparent electrode and the photo-sensitivelayer 4 to the emission conductor-2.

Reducing the Voltage through this photo-sensitive layer increases itssensitivity and linear response to light, in addition to providinglonger life and other advantages. The response time is improved, theinter-electrode capacitance effect is reduced, and the device isgenerally an improvement in the art.

The resolution of the systems herein and heretofore described depend toagreat extent on the spacing between the electron emission conductors.

This spacing is determined by the physical construction of the deviceand the interelectrode capacitance, among other factors.

One method of increasing the resolution of the electrostatic pattern andhence the visible pigment image de- 10 posited thereon is by decreasingthe space between the emission conductors.

Another method is by using several s-uch devices all controlled by lightfrom the same original ima-ge and spaced geometrically from each otherbut synchronized to form by superimposition their electrostatic patternsand images on the same web.

By longitudinally (in the direction of image receiving surface movement)displacing the devices lso that the patterns are superimposed in propergeometric location, and by laterally displacing the devices so that theelectrostatic charges from the conductors of one such device fallbetween the electrostatic patterns of said other such devices, thespacing between the electrostratic charges and hence the resolution ofthe lfinally deposited pigmented image is increased without decreasingthe spacing between individual conductors on the individual devices.

The device shown in my original application 693,690 can be termed aphoto-diode device, since it acts like an individual photo-diode at eachparallel conductor and controls the electron emission from the end ofthe conductor.

Such action is not possible from commercial transistors andphoto-diodes, because the close spacing necessary for the parallelconductors cannot be attained, since these conductors are from 0.001 to0.0005 inch in diameter and 0.005 to 0.001 inch apart in spacing.

The solid-state and vacuum devices described here operate in a mannerwhich can be loosely described as a diode-photo-diode, anddiode-photo-triode.

They have one non-light controlled electron emission source, and onelight-controlled electron emission source, the rst establishing a biaspotential not quite equal to the ionization level of the systemdescribed.

The drum shown in FIG. 19 can be a metallic drum 72 coated with aninsulating surface 71 such as an insulating plastic material of mylar,etc., or it can be a metal drum, coated with yan insulating surface,which then has conductive spots formed on it, each spot acting as aminiature capacitor, said spots being 500 to 1,000 per lineal inch, forexample.

Operation: with respect to FIGURE 17, speciiically the operation is asfollows: l

(l) Prior to the printing operation the essential parts of applic-antscircuit are lines 31 and 42, conductors 2 and 14 and that portion of theresistor between line 31 and diode 63.

(2) Applicant has utilized the inherent capacitance between theelectrodes 2' and 14 to place a D.C. bias across the printing gap (thespace between 14 and 2').

(3) The equivalent circuit of this device is a R-C circuit across abattery. As a result of the exponentially decreasing current that ilowsin the circuit the battery Volta-ge is impressed on the capacitor(printing gap).

(4) -By impinging light on photodiode (35) the printing gap now sees thesummation of the potential from line 31 to line 29. 'Discharge acrossthe printing gap is facilitated because it is necessary to only add asmall voltage to the voltage across the gap.

Having `described my invention, reference should now be had to thefollowing claims.

I claim:

1. An electron emission control device comprising an electricallynon-conductive insulating support, a multi- .plicity of conductorsretained in spaced insulated geometric relation on said support, withthe one ends of each conductor adapted to emit electrons, a means formaintaining each conductor at a constant similar minimum potential, withsaid conductors being retained in insulated relation to each other,light-sensitive semi-conducting junctions connected to said conductors,and means connecting a second potential to each conduc-tor respectivelythrough said junctions, with the resistance of said junctionsrespectively variable and dependent on the intensity of light displayedupon said junctions, and with the instantaneous potential on each ofsaid conductors individually raised above said minimum potential to avalue determined by the instantaneous resistance of said light sensitivejunction, and an accelerating electrode spaced from and parallel to theemission ends of said conductors, with the sources of electric potentialsupplied to said conductors connected so that electrons which escape theemission ends of said conductors travel in the direction of saidaccelerating electrode.

2. The device of claim 1, and a receiving surface positioned betweensaid emission ends of said conductors and said accelerating electrode,with a space between said conductor ends Iand said suface, meansilluminating an original image with light, and displaying light fromsaid image ontthe light-sensitive semi-conducting junction areasjuxtaposed tol said emission conductors, with the intensity of saidlight determining the electrical resistance of said junction and hencethe electric potential supplied to each conductor, with the constantminimum electric potential supplying a bias voltage not quite equal 'tothe ionization potential of the system consisting of the emissionconductor, the accelerating electrode, the receiving surface, and thespace lbetween, and said variable additional potential supplied eachconductor through said lightsensitive junction increasing the potentialof said individual system above said ionization level so that electronsescape said emission end of said conductor and travel in the directionof said accelerating electrode to establish an electrostatic charge onthe receiving surface opposite thereto, with the amount of said chargedetermined by the quantity of light displayed on said correspondinglight-sensitive junction, said electrostatic charges on said receivingsurface defining a predetermined electrostatic pattern determined bysaid original image.

3. In the device of claim 2, and means for depositing charged particlesupon said electrostatic pattern rendering said pattern visible.

4. An electron emission control Idevice comprising an electricallynon-conductive insulating support, a multiplicity of conductors retainedin spaced insulated geometric relation on said support, with the oneends of said conductors adapted to emit electrons, means for maintainingeach conductorat a constant similar minimum potential, with saidconductors being retained in insulated relation to each other, and meansdelivering a second constant electric potential to each conductor, withsaid conductors being retained in insulated relation to each other, andan electric field established between said second electric potential andsaid conductors, a light-sensiitive semi-conducting junction regulatingsaid control eld, a third constant electric potential connected to saidjunction said junction regulating said field, with the intensity of anyone geometric location in said control field variable at any particularinstant from any other geometric location in said eld, said intensity atany said geometric location determined by the amount of light displayed`at said corresponding location on said light-sensitive junction, saidelectric field Variably inhibiting the flow of electrons from saidsecond constant intensity potential to said conductors, with thepotential onany emission conductor at any instant individually raisedabove said minimum potential to a value permitted from said secondpotential by said corresponding control field, said control field andhence said second potential being controlled by the intensity of lightdisplayed on said corresponding light-sensitive junction, meansilluminating an original image with light, and displaying light fromsaid image on said lightsensitive junctions, an accelerating electrodeparallel to and spaced vfrom said emission ends of said conductors,connecting said first and second potentials so that electrons whichescape the emission ends of said conductors travel in the direction -ofsaid accelerating electrode, with the said firs-t minimum potential notquite equal to the ionization potential of the system consisting of theemission conductor, accelerating electrode, and space between, and saidsecond potential transferred to such conductors Variable and controlledby said electric field intermediate said second potential and saidconductors, said transferred potential being in excess of said firstconstant minimum potential.

5. The device of claim 4, and a receiving surface positioned betweensaid emission ends of said conductors and said accelerating electrodewith a space between said conductors and said surface, with anelectrostatic pattern formed on the receiving surface in response tolight from said original image, said electrostatic charges on saidreceiving surface defining a predetermined electrostatic pattern definedby said original image, said electrostatic pattern capable of being madevisible by deposition of charged particles thereon.

6. The device of claim S, and means for depositing charged particles ofiinely divided pigment upon said electrostatic pattern, forming avisible image corresponding to said original image, said particles beingcapable of being affixed permanently to said receiving surface.

References Cited UNITED STATES PATENTS 2,716,826 9/ 1955 Huebner 346-74X 2,890,923 6/ 1959 Huebner 346-74 X 2,933,556 4/1960 Barnes 34674 X2,986,442 5/1961 Broding 346-74 3,066,298, ll/ 1962 McNaney 346-743,208,076 9/1965 Mott 346-74 3,234,561 2/l966 Stone 346-74 BERNARDKONICK, Primary Examiner.

V. P. CANNEY, Assistant Examiner.

1. AN ELECTRON EMMISSION CONTROL DEVICE COMPRISING AN ELECTRICALLYNON-CONDUCTIVE INSULATING SUPPORT, A MULTIPLICITY OF CONDUCTORS RETAINEDIN SPACED INSULATED GEOMETRIC RELATION ON SAID SUPPORT, WITH THE ONEENDS OF EACH CONDUCTOR ADAPTED TO EMIT ELECTRONS, A MEANS FORMAINTAINING EACH CONDUCTOR AT A CONSTANT SIMILAR MINIMUM POTENTIAL, WITHSAID CONDUCTORS BEING RETAINED IN INSULATED RELATION TO EACH OTHER,LIGHT-SENSITIVE SEMI-CONDUCTING JUNCTIONS CONNECTED TO SAID CONDUCTORS,AND MEANS CONNECTING A SECOND POTENTIAL TO EACH CONDUCTOR RESPECTIVELYTHROUGH SAID JUNCTIONS, WITH THE RESISTANCE OF SAID JUNCTIONSRESPECTIVELY VARIABLE AND DEPENDENT ON THE INTENSITY OF LIGHT DISPLAYEDUPON SAID JUNCTIONS, AND WITH THE INSTANTANEOUS POTENTIAL ON EACH OFSAID CONDUCTORS INDIVIDUALLY RAISED ABOVE SAID MINIMUM POTENTIAL TO AVALUE DETERMINED BY THE INSTANTANEOUS RESISTANCE OF SAID LIGHT SENSITIVEJUNCTION, AND AN ACCELERATING ELECTRODE SPACED FROM AND PARALLEL TO THEEMISSION ENDS OF SAID CONDUCTORS, WITH THE SOURCE OF ELECTRIC POTENTIALSUPPLIED TO SAID CONDUCTORS CONNECTED SO THAT ELECTRONS WHICH ESCAPE THEEMISSION ENDS OF SAID CONDUCTORS TRAVEL IN THE DIRECTION OF SAIDACCELERATING ELECTRODE.